The Fat Man character was Brad Runyan, played by Jack Scott Smart who gave an excellent lighthearted performance. The series made good use of author Dashiel Hammett's name (see also Thin Man), although the author had little to do with the radio series. The name The Fat Man was the title of a chapter in the book A Maltese Falcon.

The series was later adapted in the mid-1950s. The other Fat Man was played possibly by Lloyd Berrell. Pepto Bismol comically sponsored the show for an upset stomach and to help digestion after over eating. Although the lead character Brad Runyan weighed 237 pounds, he was popular with the ladies. The cast also included Betty Garde, Paul Stewart, Linda Watkins, Mary Patton as Lila North and Vicki Vola, Dan Ocko, Rolly Bester, and Robert Dryden. The success of the old time radioseries led to a movie, The Fat Man, directed by William Castle in 1951.